Device for measurement of the bottom runner clearance in a reaction type hydraulic turbine



MITSUO T June 1, 1965 AKASE 3,186,684

DEVICE FOR MEASUREMENT OF THE BOTTOM RUNNER CLEARANCE IN A nmcnou TYPE HYDRAULIC TURBINE Filed April 4, 1963 InvEnToR matsuo 'Ekase.

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fiTTORnEy United States PatentO 3,185,684 DEVICE FOR MEASUREMENT OF THE BOTTOM RUNNER CLEARANCE IN A REACTION TYPE RAULIC TURBME Mitsno Takase, Hitachi-511i, Japan, assignor to Hitachi, Ltd, Tokyo, Japan, a corporation of Japan Fiied Apr. 4, 1963, Ser. No. 270,640 Claims priority, application .l'apan, Apr. 6, 1962, 37/ 16,755 3 Claims. (Cl. 25326) The present invention relates to an improved device for measurement of the bottom clearance of the runner in a reaction type hydraulic turbine.

It is well known that those portions of a hydraulic turbine which are continuously in contact with Water flowing therethrough are subjected to frictional wear, pitting and corrosion so that the turbine efficiency is steadily reduced during its service. Among other things, any increase in clearance at the top and bottom of the wicket gates and about the periphery of the turbine runner, causes reduc tion in the efiiciency of the turbine, which adds to the turbine corrosion problem and therefore has a direct influence upon the overall turbine efficiency. Particularly, any loss of uniformity of the peripheral clearance of the turbine runner causes unbalance of the water pressure acting upon the runner, offering a vibration problem which results in undesirable turbulencein the water passing through the turbine.

Accordingly, it is one of the most important points of attendance to the hydraulic power plant to check these clearances whenever occasion offers to enable the turbine to operate with optimum clearance values.

In practice, the clearances about the outermost periphery of the runner and at the top and bottom of the wicket gates are checked with ease directly from the inside of the turbine spiral case except with the case of small units of limited capacity.

On the other hand, particularly in case of high-head reaction turbines or like units, in which the runner is water-sealed in a number of steps, though the top clearance can be measured by inserting a gap gauge through an appropriate number of check holes arranged circumferentially in the exposed head cover, it has been difficult to arrange an appropriate number of such check holes for the lower water-sealing area, which is inside of the outermost periphery of the runner, due to the fact that the bottom cover is substantially embedded in concrete. Accordingly, only one or two check holes have previously been arranged along the passage to the manhole in the draft tube for the check of the bottom clearance. With this arrangement, it has been difficult to determine the clearance along the entire circumference of the runner with any substantial accuracy. In view of this, the present invention is intended to provide a device for measuring the clearance in the lower water-sealing area of a turbine runner with ease and accuracy, which is simple in structure.

According to the present invention, a device for measurement of the bottom runner clearance in a reaction type hydraulic turbine comprises through holes formed in the bottom cover in communication with the lower water-sealing area of the runner, and clearance measuring rooms or chambers arranged to connect said respective through holes with the inside of the draft tube of the turbine.

3,38%,634 Fatented June 1, 1965 The foregoing and other objects, features and advantages of the invention will become apparent from the following description when taken in conjunction with the accompanying drawing, in which:

FIG. 1 is a fragmentary cross-sectional elevation of a reaction turbine embodying the invention; and

FIG. 2 is a horizontal cross-sectional view taken along the line 2-2 in FIG.- 1.

Referring to the drawing, the hydraulic turbine includes a runner l, a bottom cover 2, a draft tube 3, re-

movable check covers 4 closing respective access openings formed in the bottom cover 2 below the runner 1. Clearance measuring rooms or chambers A are arranged outside :of the respective check covers A plug 5 is arranged in each of said measuring rooms A in fitting relation to a hole 6, which is arranged exactly in a position to communicate with the lower Water-sealing region g between the runner 1 and bottom cover 2. As will be understood, when it is desired to check the lower watersealing area g it is only required first to remove the check cover 4 from the inside of the draft tube 3, then remove the plug 5 arranged in the plug hole 6, and insert a gap gauge through the plug hole 6 to determine the clearance. To add, the upper water-sealing clearange g can be measured by removing the head cover, or more simply, access may be acquired from the interior of the turbine casing, as described hereinbefore. Of course, the measurement of these clearances is performed when the turbine is shut down. It will be appreciated that the provision of measuring rooms or chambers of simple structure according to the present invention makes it possible to measure the clearance in the lower watersealing area g about the entire periphery of the runner with ease and accuracy.

The invention is not restricted to the features described above and shown in the drawing but may be varied in many ways within the scope of the appendant claims.

What is claimed is:

1. In a mixed flow reaction-type hydraulic turbine having a rotary runner provided with an annular closure shroud, a guide case including a bottom cover having an annular surface spaced in close proximity to said closure shroud and overlapping the closure shroud radially at one end thereof and defining with said bottom cover an annular gap clearance space not visible from said one end due to the aforesaid overlap, a draft tube connected to said bottom cover, means to determine said clearance space comprising a plurality of axially extending holes formed in said bottom cover in alignment with said annular gap, at least one closed chamber positioned beneath said bottom cover in alignment with said holes whereby a gauge may be inserted through said holes to determine the size of said gap and means providing access to said chamber through the wall of said draft tube.

2. The combination as defined in claim 1 wherein a plurality of through holes are provided in said bottom cover spaced around the periphery of said runner and a plurality of chambers are provided in communication with said through holes.

3. In a mixed flow reaction-type hydraulic turbine having a rotary runner provided with an annular closure shroud, a guide case including a bottom cover having an annular surface spaced in close proximity to said closure shroud and overlapping the closure shroud radially at one end thereof and defining with said bottom cover an annular gap clearance space not visible from said one end due to the aforesaid overlap, a draft tube connected to said bottom cover, means to determine said clearance space comprising a plurality of axially extending holes formed in said bottom cover in alignment with said annular gap, at least one closed chamber positioned beneath said bottom cover in alignment with said holes whereby a gauge may be inserted through said holes to determine the size of said gap and means providing access to said chamber through the Wall of said draft tube, said means providing access to said chamber including an aperture in the wall of said draft tube in communication with said chamber and cover means flush with theiwall of said draft tube for closing said aperture.

References Cited by the Examiner UNITED STATES PATENTS 1,823,702 9/31 Ring 253-117 FOREIGN PATENTS 373,940 6/32 Great Britain.

JOSEPH H. BRANSON, 111., Primary Examiner. 

1. IN A MIXED FLOW REACTION-TYPE HYDRAULIC TURBINE HAVING A ROTARY RUNNER PROVIDED WITH AN ANNULAR CLOSURE SHROUD, A GUIDE CASE INCLUDING A BOTTOM COVER HAVING AN ANNULAR SURFACE SPACED IN CLOSE PROXIMITY TO SAID CLOSURE SHROUD AND OVERLAPPING THE CLOSURE SHROUD RADIALLY AT ONE END THEREOF AND DEFINING WITH SAID BOTTOM COVER AN ANNULAR GAP CLEARANCE SPACE NOT VISIBLE FROM SAID ONE END DUE TO THE AFORESAID OVERLAP, A DRAFT TUBE CONNECTED TO SAID BOTTON COVER, MEANS TO DETERMINE SAID CLEARANCE SPACE COMPRISING A PLURALITY OF AXIALLY EXTENDING HOLES FORMED IN SAID BOTTOM COVER IN DALIGNMENT WITH SAID ANNULAR GAP, AT LEAST ONE CLOSED CHAMBER POSITIONED BENEATH SAID BOTTOM COVER IN ALIGNMENT WITH SAID HOLES TO DETERMINE A GUAGE MAY BE INSERTED THROUGH SAID HOLES TO DETERMINE THE SIZE OF SAID GAP AND MEANS PROVIDING ACCESS TO SAID CHAMBER THROUGH THE WALL OF SAID DRAFT TUBE. 